Tangential thread rolling head

ABSTRACT

The invention relates to a tangential thread rolling head including two rolling head arms having a thread roll rotatably mounted on an axle. The thread rolls are configured to engage with a gear and be pushed laterally into an assembled position into the rolling head arms before the installation of the axles and the axles can be pushed into a bearing bore hole of the thread rolls. The two thread rolls have identical thread profiles that are offset with respect to each other when the thread rolls are in the assembled position.

CROSS REFERENCE TO RELATED INVENTION

This application is based upon and claims priority to, under relevantsections of 35 U.S.C. §119, European Patent Application No. 16 156541.1, filed Feb. 19, 2016, the entire contents of which are herebyincorporated by reference.

BACKGROUND

The invention relates to a tangential thread rolling head comprising twofork-like rolling head arms, in each of which a thread roll is rotatablymounted on an axle, wherein the thread rolls respectively engage with agear coupling the thread rolls, and wherein the thread rolls can bepushed laterally into an assembled position into the rolling head armsbefore installation of the axles, in which one of the axles can bepushed into a bearing bore hole of a corresponding thread roll.

A tangential thread rolling head is known, for example, from thedocument EP 0 811 443 B1. This tangential thread rolling head has theadvantage that it ensures through the complimentary configuration ofinteracting catches of thread rolls and pinions of the gear, that thethread rolls can only be installed in the rolling head arms in a singledefined rotary position. The tangential thread rolling head known fromEP 0 811 443 B1 can have rolling head arms that can be pivoted towardseach other. Tangential thread rolling heads with fixed rolling head armsthat cannot be pivoted towards each other are also known. For example,SU 654338 A1 shows such a tangential thread rolling head.

The thread rolling or respectively the cylindrical die thread rollingrecess process with tangential thread rolling heads occurs throughlateral advancement onto the workpiece to be processed up to the middleof the axle and back again. If the workpiece to be processed is locatedwith its axle on the connection line between the rotary axles of thethread rolls, the pitch points on the workpiece would arrive atlocations offset by 180°. However, this is not the case at the beginningand end of the rolling process, as will be explained below based onFIGS. 3 and 4. In order to ensure that the thread profile of a threadroll engages exactly in the thread grooves formed by the thread profileof the other thread roll, the thread profiles of the two thread rollsare spatially offset with respect to each other. This spatial offsetdimension is imperative for successful processing. Due to the demand ofthe offset dimension, it is required in the prior art to produce twodifferent thread rolls with thread arrangements that are offset withrespect to each other. The production effort is hereby increased.Moreover, a potential interchanging of the thread rolls due to theoffset thread profiles in the prior art leads to damage and loss offunctionality during processing.

Based on the explained prior art, the object of the invention is toprovide a tangential thread rolling head of the initially named type,with which the offset dimension of the thread profiles of the threadrolls required for the processing can be realized in an easier and morereliable manner from a production point of view.

BRIEF SUMMARY OF THE INVENTION

For a tangential thread rolling head of the initially named type, theinvention solves the object in that the two thread rolls including athread profile designed respectively on their circumferential surfaceare designed identically, in that the thread rolls have roll engagementmeans, which engage with the gear engagement means of the gear. The rollengagement means and the gear engagement means are configured such thateach of the thread rolls can only be pushed laterally into the assembledposition, which is a single defined rotary position. The rotary positionfor the two thread rolls is different such that the thread profiles ofthe thread rolls are offset with respect to each other in the assembledposition.

The tangential thread rolling head according to the invention has, in agenerally known manner, two rolling head arms each configured to receiveone thread roll. The rolling head arms can be held on a rolling headholder. The two thread rolls are each rotatably mounted on an axle ofeach thread roll. The rotary axles of the thread rolls run parallel toeach other. The thread rolls are joined together via a gear, such as asynchronous gear. The thread rolls can be pushed laterally into therolling head arms in order to reach the assembled position. In theassembled position, the rotary axles can be pushed into the threadrolls.

According to an embodiment, the thread rolls have roll engagement means,which engage with the gear engagement means of the gear. The rollengagement means and the gear engagement means are configured such thateach of the thread rolls can only be pushed laterally into the assembledposition in a single defined rotary position, wherein the rotaryposition for the two thread rolls is different. In the assembledposition, the thread profiles of the identically designed thread rollsaccording to the invention are thus offset with respect to each other.The roll engagement means and the gear engagement means form a geometricshape, which joins the thread rolls with the gear. According to theinvention, the geometric shapes of the two thread rolls are twisted withrespect to each other, wherein the twist represents the required offsetdimension between the thread profiles. The thread rolls and thus thestarting points of the thread profiles on the circumferential surfacesof the thread rolls are offset with respect to each other by therequired offset dimension in the assembled position. According to theinvention, the thread rolls including their thread profile are therebydesigned identically. The required offset dimension resultsautomatically and reliably in the course of the installation of thethread rolls in the tangential thread rolling head. The production ofthe thread rolls is simplified and the operational safety is increasedthrough avoidance of an interchanging of the thread rolls impacting thefunctionality.

According to a particularly practical design, the roll engagement meanscan be formed by catches of the thread rolls and the gear engagementmeans can be formed by catches of pinions of the gear. The catches ofthe thread rolls engage respective catches of a pinion. The catches ofthe thread rolls and the catches of the pinions can be configuredcomplementary to each other. The thread rolls can each have a pair ofopposite-lying catches and/or the pinions can each have a pair ofopposite-lying catches.

According to a particularly practical design, the thread rolls and thepinions can be arranged respectively on a common axle. This designfurther simplifies the assembly. For inserting the axles, the threadrolls and the pinions can each have bearing bore holes, which are flushwith each other in the assembled position of the thread rolls. Asexplained, the axles run parallel to each other.

According to a further embodiment, the catches of the thread rolls canrespectively form at least one stop surface. In the assembled positionor state the stop surfaces abut against the catches of the pinions. Forexample, in the prior art according to EP 0 811 443 B1, the problem isthat the complementary acute angles of the catch ends of thread rollsand pinions cannot be designed to be exactly the same size due tounavoidable production tolerances. As a result, the catches of thepinions are designed slightly smaller than the correspondingacute-angled seat formed by the catches of the thread rolls. The threadroll is thereby in turn pushed slightly too far into the pinion whenpushed all the way in so that the bearing bore holes of the thread rolland pinion are not exactly flush. In practice, it is then complicated topush the common rotary axle through the pinion and the thread roll. Thisproblem is overcome in the aforementioned design of the invention inthat a stop is formed by a defined stop surface and, when reached, thebearing bore holes of the thread roll and pinion are exactly flush witheach other. The assembly of the common rotary axle is correspondinglysimplified.

The stop surfaces can have a curved progression, for example acircularly curved progression. The stop surfaces can in this case beadjusted for the outer diameter of the pinion. A particularly simpleself-centering is achieved in this manner. It is also possible forexample that the stop surfaces progress into the assembled position atleast in sections diagonal to the insertion direction of the threadrolls.

Furthermore, the stop surfaces can also respectively be formed by a stopsection connecting two opposite-lying catch sections of the threadrolls. In this design, it is possible that each thread roll has only onecatch. This catch has two opposite-lying catch sections, which areinterconnected by the stop section. In contrast, the associated pinioncan have two catches.

It can be provided according to a further embodiment that the stopsections each have a smaller thickness than the opposite-lying catchsections so that a seat delimited by the stop surface is formed betweenthe opposite-lying catch sections for a complementarily catch of theassociated or corresponding pinion. A pocket-shaped seat is thus formed,delimited laterally by the ends of the opposite-lying catch sections.The floor of the seat is formed by the stop surface of the stop section.A catch of the respectively associated pinion is received in thispocket-shaped seat. According to a further embodiment, the seats of thetwo thread rolls can have different widths.

According to a further particularly practical design, the pinions andgear wheels of the gear engaging with them are provided with opticalmarkings that show the installation position of the pinions relative tothe gear wheels engaging with them. The optical markings can be formed,for example, by dotted or dashed markings applied to the pinions and theassociated gear wheels. They show the rotary position of the pinions andgear wheels provided for operating the tangential thread rolling headsuch that it is ensured in particular that the thread rolls engagingwith the pinions are installed in the provided rotary position. It canalso be provided that the gear wheels engaging with the pinions and acoupling gear wheel of the gear in turn engaging with it are providedwith optical markings, which show the provided installation position ofthe gear wheels relative to the coupling gear wheel. The opticalmarkings can in turn be formed by (further) dotted or dashed markingsapplied to the coupling gear wheel and the gear wheels.

As explained, the tangential thread rolling head according to theinvention has two rolling head arms, each of which receive one of thethread rolls. It is possible that the rolling head arms are not movablewith respect to each other, in particular are not pivotable. It is thena tangential thread rolling head with fixed rolling head arms, which canbe designed for example as one piece with a rolling head holder.Specifically in the case of such tangential thread rolling heads withfixed rolling head arms, the invention is particularly advantageoussince the thread rolls have a permanently defined position with respectto each other. The respective offset dimension can thus be realized in aparticularly reliable manner by the different specified rotary positionsof the thread rolls.

However, it is also generally possible that the tangential threadrolling head comprises a rolling head holder, on which the rolling headarms are pivotably mounted on a common axle running parallel to the rollaxles. Furthermore, the tangential thread rolling head can then haveadjusting means for adjusting the pivot position of the rolling headarms on the rolling head holder.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention are explained in more detail inthe following using the drawings. They show schematically in:

FIG. 1 illustrates a perspective view of an embodiment of a tangentialthread rolling head,

FIG. 2 illustrates a perspective view of an embodiment of a tangentialthread rolling head,

FIG. 3 illustrates a schematic representation of the processing of aworkpiece in an embodiment of the tangential thread rolling head,

FIG. 4 illustrates a further schematic representation of the processingof a workpiece in the tangential thread rolling head of FIG. 3,

FIG. 5 illustrates a perspective view of an embodiment of a gear of thetangential thread rolling head,

FIG. 6 illustrates a perspective view of an embodiment of a thread rollof a tangential thread rolling head,

FIG. 7 illustrates a perspective view of the pinion of the gear shown inFIG. 5 interacting with the thread roll from FIG. 6,

FIG. 8 is a side view of the pinion of the pinion gear shown in FIG. 5interacting with the thread roll from FIG. 6, and

FIG. 9 a top plan view of the gear shown in FIG. 5.

If not otherwise specified, the same reference numbers indicate the sameobjects in the figures.

DETAILED DESCRIPTION OF THE INVENTION

The tangential thread rolling head according to the invention shown inFIG. 1 comprises a rolling head holder 10, on which a first fork-likerolling head arm 12 and a second fork-like rolling head arm 14 aredesigned as one piece and fixed. In the first rolling head arm 12, afirst thread roll 16 is rotatably mounted on an axle 18. In the secondrolling head arm 14, a second thread roll 20 is rotatably mounted on anaxle 22. The axles 18, 22 run parallel to each other. The basicstructure and the function of such a tangential thread rolling head areknown and are thus not explained in greater detail.

FIG. 2 shows an alternative form of a tangential thread rolling headaccording to the invention. This tangential thread rolling head also hastwo rolling head arms 12′, 14′, in which the first and second threadrolls 16′, 20′ are rotatably mounted on axles 18′, 22′. In turn, theaxles 18′, 22′ run parallel to each other. In contrast to the tangentialthread rolling head from FIG. 1, the rolling head arms 12′, 14′ in thetangential thread rolling head from FIG. 2 are pivotably mounted on acommon axle 24′ running parallel to the roll axles 18′, 22′. Referencenumber 26′ shows an adjustable spring and thread means are shown (not ingreater detail), via which the pivot position of the rolling head arms12′, 14′ can be adjusted. The design and function of such a tangentialthread rolling head with pivotable rolling head arms is also generallyknown and is thus not explained in greater detail.

Based on FIGS. 3 and 4, the processing of a cylindrical workpiece shownas reference number 28 shall be explained as an example in thetangential thread rolling head in FIG. 1. FIG. 3 shows the beginning ofthe thread rolling process. The thread rolls 16, 20 and the workpiece 28are in this case advanced to each other along the infeed direction shownby the arrows 30, until the position shown in FIG. 4 is reached. Threadrolls 16, 20 and workpiece 28 are subsequently moved apart from eachother again. In FIG. 4, the first thread roll 16 engages with theworkpiece 28 along the contact location 32 and the second thread roll 20engages with the workpiece 28 along the contact location 34. The contactlocations 32, 34 lie offset by 180° with respect to each other at theprocessing time shown in FIG. 4. At the start of processing, as shown inFIG. 3, these contact locations are not offset by 180°. The theoreticalcontact location offset by 180° is shown dashed by reference number 36in FIG. 3. However, the contact of the second thread roll 20 at thestart of processing actually takes place at the contact location 34. Forthis reason, the thread profiles of the thread rolls 16, 20 must beoffset with respect to each other by a defined offset dimension, asinitially explained.

FIG. 5 shows a gear of a tangential thread rolling head according to theinvention, which can be used for example in the tangential threadrolling heads shown in FIGS. 1 and 2. The gear has a first pinion 38,which cogs with a first gear wheel 40. A second pinion 42 cogs with asecond gear wheel 44. The first gear wheel 40 and the second gear wheel44 cog with different gear wheel planes of a central coupling gear wheel46 that are movable relative to each other. The structure andfunctionality of such a synchronous gear used in tangential threadrolling heads are generally known.

The uniqueness according to the invention lies in the interaction of thethread rolls with pinions 38, 42. This interaction is explained ingreater detail based on FIGS. 6 and 8, here as an example for the threadrolls 16 and 20. This interaction takes place in a corresponding mannerfor the thread rolls 16′ and 20′. The first thread roll 16 has ahollow-cylindrical projection 48, on which two catches 50, 52 aredesigned in the shown example. Referring to FIG. 5, the first pinion 38also has a hollow-cylindrical projection 54, on which two catches 56, 58are disposed in the shown example. By pushing the first thread roll 16laterally into the rolling head arm of the tangential thread rollinghead, the catches 50, 52 (FIG. 6) of the first thread roll 16 engagewith the complementarily designed catches 56, 58 of the first pinion 38,as can be seen in FIG. 7. As shown in FIG. 5, through thecomplementarily catches 56, 58 or respectively 50, 52 (FIG. 6) thethread roll 16 (FIGS. 6-8) can only engage with the first pinion 38 in asingle defined rotary position. In this assembled position of the firstthread roll 16, a common rotary axle 60 can be pushed into the bearingbore holes of the first pinion 38 and of the first thread roll 16defined by the hollow-cylindrical projections 54 or respectively 48, ascan be seen in FIG. 8.

The second pinion 42 of the gear shown in FIG. 5 also has ahollow-cylindrical projection 62, which in turn defines a bearing borehole for a rotary axle. Two catches 64 and 66 are disposed on thehollow-cylindrical projection 62. The catches 64 and 66 are generallyidentical to the catches 56 and 58 of the first pinion 38. Moreover, thefirst and second thread rolls 16, 20 of the tangential thread rollinghead shown in FIG. 1 are configured identically, including their threadprofiles formed on the circumferential surface. The first and secondthread rolls 16′, 20′ of the tangential thread rolling head shown inFIG. 2 are also configured identically, including their thread profilesformed on the circumferential surface. However, the second pinion 42 isarranged twisted by a defined angle with respect to the first pinion 38.If the second thread roll 20 with its catches is now brought in itsassembled position engaging with the catches 64, 66 of the second pinion42 just like the first thread roll 16, the thread rolls 16, 20 are alsotwisted by this defined angle with respect to each other. The threadprofiles designed on the circumferential surface of the thread rolls 16,20 thus have a defined offset with respect to each other such that thestarting points of the thread profiles lie apart from each other by adefined offset dimension.

Referring to FIG. 9, in order to ensure the correct installation of thepinions 38, 42 in the correct rotary position, a corresponding markingcan be provided on the tangential thread rolling head and on the pinions38, 42, which is to be appropriately noted by the processor duringinstallation of the pinions 38, 42. This is explained in FIG. 9 based onan example. Dot markings 68, 70 are in this case detected on the pinions38, 42 as well as the gear wheels 42, 44 engaging with them. Thesemarkings 68, 70 display the provided installation position of thepinions 38, 42 and gear wheels 42, 44 with respect to each other.Moreover, the gear wheels 42, 44 have second dot markings 72, which canbe brought to overlap correspondingly with dot markings 74 of thecoupling gear wheel 46 during the installation of the gear. It isensured in this manner that the pinions and gear wheels of the gear arecombined in the correct rotary position and the thread rolls are thusalso inserted in the provided rotary position with the required offsetdimension.

REFERENCE LIST

-   10 Rolling head holder-   12 First rolling head arm-   12′ First rolling head arm-   14 Second rolling head arm-   14′ Second rolling head arm-   16 First thread roll-   16′ First thread roll-   18 Axle-   18′ Axle-   20 Second thread roll-   20′ Second thread roll-   22 Axle-   22′ Axle-   24′ Axle-   26′ Adjustable spring-   28 Cylindrical workpiece-   30 Arrows-   32 Contact location-   34 Contact location-   36 Theoretical contact location-   38 First pinion-   40 First gear wheel-   42 Second pinion-   44 Second gear wheel-   46 Coupling gear wheel-   48 Hollow-cylindrical projection-   50 Catch-   52 Catch-   54 Hollow-cylindrical projection-   56 Catch-   58 Catch-   60 Rotary axle-   62 Hollow-cylindrical projection-   64 Catch-   66 Catch-   68 Dot marking-   70 Dot marking-   72 Dot marking-   74 Dot marking

1. A tangential thread rolling head comprising: two thread roll arms;two thread rolls having identical circumferentially disposed threadprofiles, each thread roll defining a bearing bore hole and configuredto be rotatably mounted on an axle, wherein each thread roll engages agear coupling the thread roll and can be pushed laterally into anassembled position into the rolling head arms before installation of theaxle, and wherein one of the axles can be pushed into the bearing borehole of a thread roll; and a roll engagement means configured to engagea gear engagement means of the gear, the roll engagement means and thegear engagement means configured to only allow the two thread rolls tobe installed in a single defined rotary position, wherein the singledefined rotary position of the two thread rolls offsets the identicalcircumferentially disposed thread profiles with respect to each other.2. The tangential thread rolling head according to claim 1, wherein theroll engagement means are formed by catches of the thread rolls and thegear engagement means are formed by catches of pinions of the gear. 3.The tangential thread rolling head according to claim 2, wherein thecatches of the thread rolls and the catches of the pinions arecomplementary to each other.
 4. The tangential thread rolling headaccording to claim 2, wherein the thread rolls and the pinions aredisposed on a common axle.
 5. The tangential thread rolling headaccording to claim 2, wherein the catches of the thread rolls each format least one stop surface, wherein the at least one stop surface abutsthe catches of the pinions in the assembled position.
 6. The tangentialthread rolling head according to claim 5, wherein the at least one stopsurface is formed by a stop section connecting two opposite-lying catchsections of the thread rolls.
 7. The tangential thread rolling headaccording to claim 6, wherein each stop section has a smaller thicknessthan the opposite-lying catch sections so that a seat delimited by thestop surface is formed between the opposite-lying catch sections andconfigured to engage a complementarily catch of a corresponding pinion.8. The tangential thread rolling head according to claim 7, wherein thepinions and corresponding gear wheels of an engaging gear includeoptical markings configured show a proper installation position of thepinions relative to the gear wheels engaging them.
 9. The tangentialthread rolling head according to claim 1, wherein the two rolling headarms are not movable relative to each other.